linux-kernel - [PATCH 3.16 181/305] ARM: 8578/1: mm: ensure pmd

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Date:	Sat, 13 Aug 2016 18:42:51 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Russell King" <linux@...linux.org.uk>,
	"Catalin Marinas" <catalin.marinas@....com>,
	"Steve Capper" <Steve.Capper@....com>,
	"Russell King" <rmk+kernel@....linux.org.uk>,
	"Will Deacon" <will.deacon@....com>
Subject: [PATCH 3.16 181/305] ARM: 8578/1: mm: ensure pmd_present only
 checks the valid bit

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Will Deacon <will.deacon@....com>

commit 624531886987f0f1b5d01fb598034d039198e090 upstream.

In a subsequent patch, pmd_mknotpresent will clear the valid bit of the
pmd entry, resulting in a not-present entry from the hardware's
perspective. Unfortunately, pmd_present simply checks for a non-zero pmd
value and will therefore continue to return true even after a
pmd_mknotpresent operation. Since pmd_mknotpresent is only used for
managing huge entries, this is only an issue for the 3-level case.

This patch fixes the 3-level pmd_present implementation to take into
account the valid bit. For bisectability, the change is made before the
fix to pmd_mknotpresent.

[catalin.marinas@....com: comment update regarding pmd_mknotpresent patch]

Fixes: 8d9625070073 ("ARM: mm: Transparent huge page support for LPAE systems.")
Cc: Russell King <linux@...linux.org.uk>
Cc: Steve Capper <Steve.Capper@....com>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm/include/asm/pgtable-2level.h | 1 +
 arch/arm/include/asm/pgtable-3level.h | 1 +
 arch/arm/include/asm/pgtable.h        | 1 -
 3 files changed, 2 insertions(+), 1 deletion(-)

--- a/arch/arm/include/asm/pgtable-2level.h
+++ b/arch/arm/include/asm/pgtable-2level.h
@@ -163,6 +163,7 @@ static inline pmd_t *pmd_offset(pud_t *p
 
 #define pmd_large(pmd)		(pmd_val(pmd) & 2)
 #define pmd_bad(pmd)		(pmd_val(pmd) & 2)
+#define pmd_present(pmd)	(pmd_val(pmd))
 
 #define copy_pmd(pmdpd,pmdps)		\
 	do {				\
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -212,6 +212,7 @@ static inline pmd_t *pmd_offset(pud_t *p
 						: !!(pmd_val(pmd) & (val)))
 #define pmd_isclear(pmd, val)	(!(pmd_val(pmd) & (val)))
 
+#define pmd_present(pmd)	(pmd_isset((pmd), L_PMD_SECT_VALID))
 #define pmd_young(pmd)		(pmd_isset((pmd), PMD_SECT_AF))
 
 #define __HAVE_ARCH_PMD_WRITE
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -182,7 +182,6 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD
 #define pgd_offset_k(addr)	pgd_offset(&init_mm, addr)
 
 #define pmd_none(pmd)		(!pmd_val(pmd))
-#define pmd_present(pmd)	(pmd_val(pmd))
 
 static inline pte_t *pmd_page_vaddr(pmd_t pmd)
 {